Studies are being conducted to examine the intestinal epithelial mechanisms of infantile soybean protein (SBP) intolerance. We have hypothesized that SBP intolerance arises from a primary interaction between components of the soybean complex and galactosyl or glactosaminyl receptors at the intestinal epithelial surface. Interactions by soybean fractions with the membrane are being investigated using rabbit mucosal tissues and rabbit red blood cells. The results suggest a complex interaction between soybean lectin, soyasaponin and glycinin at the level of the enterocyte apical membrane. Soybean lectin destabilizes the membrane toward soyasaponin-induced lysis. Soyasaponin enhances the entry of glycinin into the epithelial cells. The membrane mechanisms involved in these processes are being investigated.